Alternator output of M25XP 1989?

[Chris Martinson]

I am a third owner of my boat and the manuals are long gone and there are no markings on my alternator - it appears original or at least old....does anyone know the output?

Much thanks

Chris Martinson
More Therapy
Hull 945

[Stu Jackson]

Chris,

Most likely a 55 amp internally regulated Motorola.  FWIW, there were no manuals about that part of the boat system, just the wiring diagrams for the panel and the AC DC systems, that you can find on the main homepage (http://www.c34.org/) under Manuals tab on the left side index.

Of course, with the OEM setup, you will get nowhere near 55 amps out of it.  Suggest you read Jim Moe's article on the electrical systems at:  http://www.c34.org/projects/projects-electrical-system-upgrade-2.html

Maine Sail has recently done some testing, claiming that internal regulators will work almost as well as Balmar and others external three stage regulators.  See his post at: http://catalina36.org/eve/forums/a/tpc/f/6186056212/m/6081030442

[Ken Juul]

Stu,
Can you post the C36 article as an attachment rather than a link. Many of us don't have accounts with the C36 site.

[mainesail]

Stu,

The regulator I'm talking about is the Leece-Neville adjustable regulator 8RG2043. I can't say if the standard internal regulator on the stock alternator would work as well and I doubt it since the MR series Leece-Neville's were built for marine applications as is the adjustable regulator. There is a slight difference in the bulk phase of roughly 10 minutes more to get from 50% charge to 90% charge, on my two 4D batteries, and it cold be slightly longer with more ah capacity with the Leece-Neville regulator but it's not a huge issue. The question you have to ask is is it worth the $300.00 more and the potential reliability issues, like I've had, with the Balmar regulators. I honestly don't find a slight loss in bulk worth the headache of my two failed ARS series regulators or the conversions to external etc..

Here's the link to my article but it does not mention to much about the regulators just a small blurb although I should edit it.. http://www.pbase.com/mainecruising/catalina_36_alternator

[Stu Jackson]

Ken, from the C36 site:  The ? was:  "Can a 3 stage regulator be installed on a stock Motorola alternator?" 

We'd discussed this earlier, (see: http://c34.org/bbs/index.php?topic=666.0) based on a question I asked that a friend had asked me.  Our conclusion was why bother, since you'd want to upgrade the alternator, not just its output and that the 55 OEM wasn't really designed to produce max amps.  The 55 OEMs were originally installed for the really "goode olde days" when all batteries had to do was run a few lights.  Things are different now with larger and more continuous electrical loads (like fridges). 

Here's Rodds' reply from the C36 thread:

Yes with the right adapter plate but why? It's only a 51 or 55 amp.. For more info read this article: Catalina 36 Alternator Installation (http://www.pbase.com/mainecruising/catalina_36_alternator)
That was the install on my 36 and I had that ARS-4 fail on me with a faulty connection in the PC board.

On my new boat a C-310 I also installed that same alternator but this time with an ARS-5 and it too failed after 2 months with the same diagnosis a failed and faulty circuit board connection. While it was in for repair I re-installed the regulator that came with the Leece-Neville alternator and to my surprise the charging characteristics were very similar when measured with my Xantrex XBM. It charged my two 4D batteries from 50% discharge to 90% charge taking only 10 minutes longer and the rate of charge from 90% on up was identical including the float voltage. I never did re-install the ARS-5 on my current boat and have been charging just fine with my built in regulator and 90 amp alternator. The reliability for me was the clincher with the Balmar units two for two is poor performance in my book and I can live with a 10 minute longer charge time from 50% to 90% if it's more reliable..

Maine Sail
http://www.pbase.com/mainecruising 

As noted the BIG difference is that the LN is an internal but ADJUSTABLE regulator.

[mainesail]

Here's a picture of the regulator that comes on the 90 amp Leece-Neville. You can see the adjustment screw for adjusting the output voltage in the cut out in the round labeling sticker. While it is tough to adjust this screw while the alternator is mounted, because of the heat exchanger, I figured out a way. To adjust it, in place, I heated up a small flat blade screw driver with a blow torch and then bent the tip 90 degrees in my vice and it works great! This regulator  has worked very well for me. I suppose if I was running Gels or AGM's I still might opt for another external regulator but with wet cells I don't see the need..

[Chris Martinson]

Thank you for the info

Chris